Nutritional budget for the freshwater snail Bithynia graeca (Gastropoda: Bithyniidae)

Abstract

The nutritional budget of B. graeca was studied using samples of a snail population of Lake Kerkini (N. Greece). The highest daily rates of consumption, faecal production and assimilation were observed in newly hatched snails and the lowest rates in mature snails. It was assumed that this snail feeds exclusively on the aufwuchs, which was abundant in the study area, and estimates of annual consumption and annual faecal production (per m2) in the field were derived. Accordingly, the annual consumption rates were 218.9 g dry weight of aufwuchs/m2 in females, and 227.7 g in males; similarly, the annual rates of faecal production were 101.8 g dry wt/m2 in females and 99.2 g/m2 in males. The assimilation efficiency for all size classes was found to be 53.5% in females and 56.4% in males.